Revert "Simplify the use of `phutil_get_library_root`"
Revert "Simplify the use of `phutil_get_library_root`"

Summary:
This reverts commit 67a17d0efb025665237d0d174d55d1887f9a6064.

This doesn't actually work because the call to `phutil_get_current_library_name()` always occurs within `libphutil`.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D13187

julkiewicz/libphutil,julkiewicz/libphutil,julkiewicz/libphutil